In most double-cassette tape players used in automatic telephone answer apparatuses, cassettes loaded therein are driven selectively so as to use one of the reproduce an automatic answer message and the other to record and reproduce messages of telephone calls.
Most prior art driving units for use in a double-cassette tape player in a telephone answering apparatus include a pair of driving units each loaded with each of a pair cassette halves and each including reel bases, a capstan rotatably driven at a constant speed, a pinch roller compressing a tape to the capstan to drive it, and a magnetic head associated with each cassette In such a double-cassette tape player, however, when used in a telephone answering apparatus, respective cassette loading units are driven selectively and not simultaneously, and only one set of amplifier is provided in most cases. Therefore, in order to balance the reproduced sound volumes, etc. of two cassettes, it is necessary to carefully select two magnetic heads not largely different in their characteristics before incorporating them into the unit. This invites some difficulties in magnetic head selecting and assembling processes. Further, the use of two magnetic heads in a single unit results in an increase of parts and the manufacturing cost.
If a single magnetic head can be used commonly for a pair of cassettes, this leads to a reduction of the number of the magnetic heads and alleviates such a process of selecting magnetic heads. In order to use a single magnetic head for both cassettes, however, it is necessary to move the single magnetic head selectively to tape exposed portions of a pair of cassettes and further to positions for contact with magnetic tapes in the cassettes. Therefore, a driving unit using a single head for two cassettes requires a plurality of drive sources for driving in different directions a head base supporting the magnetic head thereon, and this invites a complicated structure of the unit.
In this connection, the inventors of the present invention formerly proposed a driving unit for a double-cassette tape player using a single magnetic head and capable of moving the magnetic head in different directions by a single motor as disclosed in Japanese Utility Model Application No. 62-18520. FIG. 17 shows the prior art application. In the driving unit designed for receiving microcassettes, a chassis 81 has two cassette receiving areas A and B which receive cassettes Ca and Cb respectively, with their tape-exposed portions being faced downwardly in the drawings. The cassette receiving area A is provided with a pair of reel bases 82a and 82b and a capstan 83, whereas the other cassette receiving area B is provided with a pair of reel bases 84a and 84b and a capstan 85. The chassis 81 is further provided with a slide member 86 which is slidably movable in the X-Y direction. The slide member 86 is provided with a head base 87 which is supported by a guide groove 86a formed in the slide member 86 for slidably movement in the A-B direction. The head base 87 supports thereon a magnetic head 88 and a pinch roller 89. When a recording or reproducing operation is effected against the cassette half Ca on the cassette receiving area A, the head base 87 is moved in the A-direction, and the slide member 86 is subsequently driven in the X-direction to bring the magnetic head 88 into contact with the magnetic tape in the cassette Ca and to urge the pinch roller 89 against the capstan 83 to closely sandwich the magnetic tape therebetween and make it travel in the cassette Ca. When a recording or reproducing operation is effected against the cassette Cb in the cassette receiving area B, the head base 87 is moved in the B-direction, and the slide member 86 is subsequently driven in the X-direction to bring the magnetic head 88 into contact with the magnetic tape in the cassette Cb and to urge the pinch roller 89 against the capstan 85 to closely sandwich the magnetic tape therebetween and travel it in the cassette Cb.
In a driving mechanism for driving the slide member 86 and the head base 87, a change gear is rotated in forwarded and reverse directions by a single motor to move the head base 87 in the A- or B-direction and move slide member 86 in the X- or Y-direction. This arrangement is common to an embodiment of the invention and will be described in detail later with reference to an explanation of an embodiment, so its detailed explanation is omitted here.
In a system using a single motor to drive the slide member 86 and the head base 87 as in the aforegoing prior art, the motor must be properly controlled by always detecting the present mode, i.e. where the slide member 86 is positioned in the X-Y direction, and where the head base 87 is positioned in the A-B direction. For the purpose of this detection, the aforegoing prior art UM application No. 62-18520 uses a leaf switch to detect in which direction the slide member 86 is moved and in which direction the head base 87 is moved.
This detection method, however, requires a number of switches to precisely detect positions of the head base 87, etc. and causes a complicated structure of the system. Additionally, since a chatering region is inevitable between On-Off conditions in such a leaf switch, it is difficult to establish a precise or acurate timing. Further, upon a power-on of the power supply subsequent to a stop condition, a mechanism of this type must acknowledge the present mode of the unit. However, in order to arrange the leaf switch to effect this acknowledgement and an initializing operation, a number of further switches and a complicated control circuit are required.
It is therefore a first object of the invention to provide a mode detection apparatus for a double-cassette tape player which can establish a detection mechanism capable of precisely detecting respective modes and capable of precisely effecting an initializing operation subsequent to a power-on, but does not invite a great increase in the number of parts or in the mounting space.
In the mechanism such as the aforegoing prior art U.M. application No. 62-18520 using a single motor to drive the head base 87 and the slide member 86, a slip mechanism is required between a driving mechanism of the head base 87 and a driving mechanism of the slide member 86 in order to establish relative timings of their motions. The use of the slip mechanism, however, often causes a relative displacement between the head base 87 and the slide member 86 caused by an undesired slip of the slip mechanism when an external force is applied to the head base 87, etc. This phenomena is not readily detected precisely by the prior art detection apparatus using a leaf switch. As a result, the prior art detection apparatus often misunderstands that the head base 87 has fully moved although it is actually located between both cassette receiving areas A and B, and hence permits the slide member 86 to move in the X-direction. As a result, the head base 87 in a halfway position is moved in the X-direction and locked there. Then the unit falls in an unreturnable configuration.
It is therefore a second object of the invention to provide an error motion preventing apparatus in a double-cassette tape player which can precisely detect positions of the head base and the slide member, can detect a locked condition upon a movement of the slide member toward the cassette receiving area before a full movement of the head base to the cassette receiving area caused by a relative displacement between the head base and the slide member upon an accidental slip of the slip mechanism, and can subsequently return the mechanism to a proper configuration.